In recent years, small and light-weight electronic devices have been actively developed. A liquid crystal display device mounted on such an electronic device is required to consume low power. One driving method that reduces the power consumption of a liquid crystal display device is “idled driving”, involving a driving period in which scan lines are scanned and signal voltages are written, and an idle period in which all the scan lines are left unscanned and writing does not occur. In the context of idled driving, control signals and the like are not provided to the scan line drive circuit and/or signal line control unit during an idle period such that the scan line drive circuit and/or signal line control unit do/does not operate, thereby reducing the power consumption of the liquid crystal display device. Such idled driving is also called “low-frequency driving” or “intermittent driving”.
In a liquid crystal panel used in a liquid crystal display device, applying a voltage between pixel electrodes and the common electrode sandwiching the liquid crystal layer changes the orientation of liquid crystal molecules (i.e. their longitudinal direction) due to the dielectric anisotropy of liquid crystal. Further, since liquid crystal has optical anisotropy, a change in the orientation of liquid crystal molecules changes the polarization direction of light passing through the liquid crystal layer. Thus, a voltage applied to the liquid crystal layer controls the amount of light passing through the liquid crystal layer to display an image on the liquid crystal panel.
However, a response of liquid crystal to a change in applied voltage requires a certain time. For example, in liquid crystal display devices based on twisted nematic (TN), in-plane switching (IPS) and vertically aligned (VA) techniques, which are currently widely used, a response of liquid crystal may require a period of time of about 50 ms. Further, the response speed of liquid crystal changes depending on temperature, where the response time decreases as the temperature decreases.
Further, when the frequency of image signals is 60 Hz, one frame period is 16.7 ms. Thus, if the response time of liquid crystal is longer than one frame period, an afterimage is produced on the screen, decreasing the display quality of images.
In view of this, JP 2004-4629 A (Patent Document 1) and JP 2011-170327 A (Patent Document 2), for example, disclose liquid crystal display devices in which “overshoot driving” occurs, that is, a voltage greater than a voltage that is originally to be applied to the liquid crystal layer is applied thereto. For overshoot driving, a lookup table (referred to as “LUT” or “table”) is used that stores correction values associated with combinations of gray scale values of preceding frames and gray scale levels of current frames. That is, a correction value associated with a combination of the gray scale value of a preceding frame and the gray scale value of a current frame is read from the LUT, and this correction value is used to correct an input image signal, and the resulting corrected image signal is output. This corrected image signal is used to perform overshoot driving to increase the display speed of the liquid crystal display device.